The invention relates to a method of producing a metal section as used, for example, in the construction industry, in window construction, in the construction of vehicles or machines or similar application areas.
The known metal sections are generally produced from a piece of metal by rolling processes. A drawback of the known metal sections is that of having the same material thickness on all limbs of the profile, even though the loading requirements frequently only require a high level of stability in one axis, for example, as a resistance to bending. The material present in the axis which is subject to a lower degree of loading is unnecessary and leads to material being wasted and higher costs. In addition, in conventional rolled sections the limbs in, for example, the y-axis cannot be arranged in any desired manner, since it is still necessary for it to be possible to roll the subsequent section, as a result of which the limb in the y-axis cannot be arranged in the vicinity of the static optimum, i.e. approximately in the centre of a section.
Moreover, the production method may lead to the material being weakened by buckling or bending of the material. Moreover, desired metal sections are frequently impossible to produce owing to the fact that metals can only be rolled up to certain material thicknesses. In addition, it is not possible to produce metal sections corresponding to the individual required use with interrupted section limbs or with section limbs arranged longitudinally, transversely, diagonally, in curves or in some other manner. Even extruded sections, as are illustrated, for example, in a production method shown in the Document DE 30 25 706, are generally only produced from relatively expensive material, such as for example aluminium, and in addition, owing to the complicated manufacturing processes, are expensive and sometimes have to be sized again. Such pre-sized metal sections are unable to eliminate the abovementioned drawbacks in the production process. The known casting processes for metal sections are also expensive. A production method for sections made of castings is illustrated, for example, in the Document DE 448 116. In this method it is only possible to process section limbs which are produced on the rolling mill trains in the foundry from still glowing material. The method shown is still dependent on expensive tools in the foundry and is unsuitable for subsequent cold working or for metal sections with relatively intricate contours. In areas such as, for example, window construction, a multiplicity of different metal sections have to be processed in quick succession in accordance with the requirements on load-bearing capacity. In order to be able to cover the materials requirement, expensive storage and logistics are required. The processor is dependent on the correct sections being supplied at the correct time. In addition to the strength of limbs of a metal section in one axis, the requirements placed on individual section limbs may, however, also differ from one another in other ways, such as for example by sound and/or heat insulation, electrical conductivity, decorative coating, corrosion protection, defined buckling or crash behaviour in automotive construction or certain advantageous contours in terms of shaping and design integration, which requirements, however, owing to the technical features of currently known metal sections, can only be achieved by expensive re-machining of the finished sections or cannot be achieved at all. Also, combining section limbs made of different materials with one another, and specifically not only metallic materials, such as iron, copper, aluminium, alloys, etc., but also other materials, such as for example ceramic, glass, plastics, wood, etc., is currently possible only using expensively preformed parts and/or section limbs which can be joined with considerable assembly outlay such as by screwing, welding, adhesive bonding, etc.
In order to overcome the above-described drawbacks which result from the prior art, the object of the present invention is to provide a cost-effective method of producing metal sections which as a priority permits high throughputs, low tool wear and reliable joining of the section limbs while making the production method and the sections which can be produced thereby as variable as possible.
The object according to the invention is achieved by means of a production method in which firstly a groove is made in another section limb by means of a microstructure-changing material deformation, then the abutting side of a section limb of the metal section is positioned in the groove situated on the inside of the other section limb and then, by means of a pressure at which the flow limit of the material situated beneath the said groove is exceeded, the material, situated next to the groove, of the other section limb is directly or indirectly caused to move towards the side faces of the one section limb to such an extent that at least a force-fitting join is achieved at the contact locations. If a groove is of wide enough design, it is also possible according to the invention to attach more than one section limb in a groove in a microstructure-changing manner.
In a further refinement of the invention, the groove is made and/or the material, situated next to the groove, of the other section limb is subsequently pressed onto the side faces of the one section limb by means of suitably shaped pressure rolls, along which the section limbs, which are placed one inside the other, pass and/or beyond which the section limbs move. However, it is also possible for the groove to be made and/or the material, situated next to the groove, of the other section limb to be pressed on by means of the stroke movement of a suitable and suitably shaped tool. The profile limbs may comprise any desired flat material or semifinished products. The channel depth and/or width of the groove may be smaller at one point of a cross-section than at another point, so that one or more protruding teeth are formed, the front edges of which press into the material of the one section limb during the microstructure-changing attachment or, in the event of a corresponding positive/negative shaping of the parts to be attached to one another, mesh with one another. Such a design of the groove may, for example, be achieved by means of a plurality of correspondingly angled and shaped pressure rolls or by bending up the other section limb prior to the microstructure-changing introduction of the groove and then bending it back.
Moreover, it is possible for the groove situated in the other section limb and the material, penetrating into the groove, of the one section limb to be at an angle to the vertical axis of the one section limb or for the vertical centre axis of the groove not to be at right angles to the horizontal surface of the other section limb, in order to achieve a greater contact area between the materials to be joined or to optimize the introduction of forces in the desired manner.
In addition to the introduction of the groove, it is possible for suitably shaped and aranged tools to machine at least one of the side walls of the groove in such a manner that the frictional resistance is increased in a manner known per se, such as for example by notches, perforations, roughening, graining, which effect can be achieved by rolls or else by stroke-executing tools. It is also possible, for example, in the same way to compress the underside of the penetrating section limb at least on one side and/or in an at least partially widening manner, or to effect other measures which increase the frictional resistance, such as notches in the longitudinal and/or transverse directions, perforations, graining, stamping, roughening and/or making projections in the section limb to be placed in the groove. However, machining which increases the frictional resistance may also be carried out by other means which are known per se, such as for example tools of other than rolls, for instance single-point tools, press tools, etc., or chemical processes such as etching. The proposed treatment of the groove and/or of the side faces can be carried out variably in differing thicknesses at differing intervals, intermittently, alternately or in some other manner. The machining which increases the frictional resistance may be carried out in a manner in which not only are the sliding forces between the surfaces resting on one another increased, but also, in addition to the force fit, a form fit is achieved between the surfaces resting on one another. Instead of, or as well as, the treatment which increases the frictional resistance, the section limb to be inserted may be microstructurally changed or upset in the region of the insertion depth or even above this, in order to create a form-fitting join or desired defined force ratios following the microstructure-changing attachment to one or more other section limbs.
During the microstructure-changing impressing of the groove and during the subsequent pressing onto the side faces, the section limbs are supported by retainers. In the case of stroke-executing tools, the support may be provided by simple plates as retainers, while in the case of conveying systems with an advance over rolls, the support also has to be effected by mobile retainers, preferably by rolls. In the case of smooth section limbs, the supporting surfaces of the retainers should likewise be of smooth design, unless it is desired to achieve an additional shaping of a section limb over and above the introduction of the groove or the pressing-on of the adjacent material. A profile limb machined by pressure rolls may then, for example, be supported on the other (rear) side by negatively shaped pressure rolls, which permits an additional shaping process to the microstructure-changing deformation for the purpose of attaching the machined section limbs. Thus it is possible to incorporate projections, bulges, beads, etc., into a section limb. Before, during or after the microstructure-changing attachment, it is possible for one or more section limbs of the metal section to receive machining and/or coatings which increase the stiffness, provide insulation, inhibit corrosion, reduce the weight, create desired breaking points or provide decoration. One or more section limbs may also, on one or alternate sides, be indented by shearing or provided with beads, in order, for example, to increase the torsional stiffness. An insulating coating of one or more section limbs may be realized using suitable materials, in order to achieve a desired mechanical, thermal, acoustic or electrical characteristic of the metal section. To prevent corrosion, it is possible for the profile limbs to have been or be completely or partially galvanized, lacquered or treated or coated in some other manner. In a further refinement of the invention, the corresponding machining and/or coatings are performed before or during passage through the microstructure-changing attachment. The appropriate tools may be accommodated in exchangeable magazines which permit rapid tool change and therefore high flexibility. However, should machining or coating during passage through the installation for microstructure-changing attachment be impossible or uneconomical, for whatever reason, these operations can also be performed subsequently. The production method according to the invention has the advantage that coatings suffer only relatively little damage during the microstructure-changing attachment. Suitable decorative coatings are, for example, a plastic coating, laquering, chrome-plating or gold-plating.
In a further refinement of the invention, the pressure rolls press the material, situated next to the groove, of the other section limb upwards at the side faces of the one section limb, in order to provide a larger contact and support area. Furthermore, it is proposed to sever one or more metal strips, which are further processed to form a section limb of a metal section, from a sheet-metal coil by means of pressure-exerting or cutting tools. The pressure-exerting or cutting tools may in this case themselves or using additional pressure-exerting or cutting tools, by means of a suitable design of the machining surface, additionally create notches and/or machining which increases the frictional resistance in the surfaces of the section limbs which are to be severed. In order to permit high processing rates, tools designed as rolls are proposed.
It is also possible to employ stamping tools which operate with a stroke movement instead of, or as well as, rolling tools, which permit a rolling production method, for the method steps according to the invention. Stamping tools are advantageous if machining is not required over the entire length of a section or if it is intended to operate with less expensive tools and/or at lower machining rates. In principle, in terms of the production of a microstructure-changing attachment according to the invention, there is no difference between tools operating by rolling and tools operating by stamping strokes. In order to increase the holding forces of the microstructure-changed join, but also in order to increase acceptance of the novel attachment technique or to fulfil statutory approval conditions or in order to be able to achieve other industrial advantages, it is possible additionally to reinforce the join by joining techniques which are known per se, such as for example adhesive bonding, riveting, welding.
It is possible for further, third material, for example in the form of wire, pieces of sheet metal, adapter pieces for filling excessively wide grooves or insulating material, to be introduced into the groove and applied to at least one side face of the one section limb, by means of microstructure-changing attachment, instead of, or as well as, the adjacent material of the other section limb. Such a procedure is conceivable, for example, if insufficient material is available for the microstructure-changing attachment owing to the depth of the groove being too small, if it is desired to make a particularly large slope, or if it is intended to introduce different, for example, harder material. It is also possible for suitably shaped third material, for example in the form of a wedge, to have a positive effect on the form fit of a microstructure-changing attachment.
The microstructure-changing attachment work-hardens the material which it affects. The material of at least one section limb attached in a microstructure-changing manner may, however, also be additionally work-hardened or hardened in some other manner subsequently. The section limbs attached in a microstructure-changing manner may be fully or partially coated before or after the attachment operation. The sections attached in a microstructure-changing manner may be canted previously or subsequently in any desired way and/or be deformed in any desired manner. The microstructure-changing attachment of the two or more section limbs to one another may be performed continuously but also in an interrupted manner on only one or more portions of the metal section, in teeth, curves, laterally offset, alternatingly or in any other desired manner. The groove may be formed continuously, but it is not necessary for a section limb to be placed continuously in the groove or for the adjacent material to be pressed on continuously. The material may be divided into short partial pieces or, depending on the individual pieces, may change as working material.
Moreover, the proposed method can be used to attach to a metal section further parts made of metal, glass, rubber, plastic, ceramic or other materials as section limbs or some other part to at least one of the section limbs in a microstructure-changing manner for decoration, sealing or for some other purpose and/or to join together two or more profile limbs, for example as a spacer or insulating web. As a result it is possible, for example, to arrange on the metal section acoustic, electrical, thermal or other insulations, housings, claddings, instruments or means for joining to other sections, covers or other shaped articles without additional attachment means, such as screws, rivets, etc.
At least in portions, the one section limb does not necessarily have to be attached to the other section limb, using the microstructural change, in a straight line but may also be attached thereto in a laterally offset line, such as for example in wave form, diagonally, transversely and/or in an interrupted manner. In combination with deformations and bevels which are possible before or afterwards, in theory it is possible by means of the method according to the invention to achieve all conceivable shapes and cross-sections of the section. Individual profile limbs can be pre-cut, stamped, laser-cut in a curved contour or may be pre-contoured in some other manner before they are attached to another section limb in a microstructure-changing manner, in order to produce a semi-circular arc or a rounded section. The section limbs may also, on one side along the longitudinal axis, be stamped, drawn, compressed, and/or rolled on the other side, in order to achieve bending of a section limb. Bimetallic limbs may also be used to achieve a desired thermal performance or the profile limbs are assembled at different temperatures, in order at a then identical temperature to achieve a specific material stress. For certain applications, such as for example girders in building or facade construction, the profiles have to exhibit a specific preloading, in order, under load in the installed condition, to correspond to a straight line. Such preloadings may be introduced into the section according to the invention in the manner described. It is thus possible to form, in any desired sequence, every conceivable shape of section using the operations describedxe2x80x94including sheet-metal machining in progressive tools to achieve a desired shape of a section limb, such as for example in automobile construction.
The strength of the microstructure-changing attachment can be additionally increased if the one section limb placed in the groove is cooler than the other section limb before the two section limbs are atached to one another in a microstructure-changing manner. The other section limb is heated when a groove is made therein. If a cooler one section limb is placed in this groove, the two limbs are fastened to one another in a microstructure-changing manner and the other section limb is then cooled, the material of the latter then contracts, as a result of which the clamping action of the microstructure-changing attachment is assisted in a positive manner. This effect can be reinforced or replaced by a controlled heating or cooling of entire section limbs or parts thereof. If the groove is made as an undercut, the result is clamping lugs which protrude at the side walls of the groove, as a result of which a form-fitting join can be achieved in addition to the force-fitting join during the subsequent microstructure-changing pressing on. The form-fitting join can be additionally or only supported by shaping the section limb to be placed in the groove. An additional form-fitting join provides the advantage that it continues to exert holding forces if the holding forces provided by the force-fitting join should wear off for reasons of chemical, thermal, mechanical or some other action.
As an additional or alternative means for the microstructure-changing attachment, the materials to be joined together in the region of the groove can be joined together using a ram-striking process operating at high frequency. In the process, the material at the joining location is driven apart, deformed, and possibly almost welded together by the high-frequency movement. A groove which widens as its depth increases, in which groove the material can diverge and as a result is particularly well secured in a form-fitting manner against being subsequently detached from the join, has proven particularly advantageous here. The object of the high-frequency ram-striking process is for the materials of the section limbs to be attached to one another to become intermingled or interlayered as far as possible. A high-frequency treatment of a section limb or of the entire section may also advantageously be used to reduce inherent stresses or to produce a stabilized inherent stress.
The method according to the invention makes it possible to produce large quantities of the novel metal section quickly and cost-effectively at low tool costs, it being possible for the section limbs to be arranged virtually as desired with respect to one another and also for material of different thicknesses, even bar or block material, to be processed into a metal section. It is thus possible to adapt the metal section to the prevailing loads, leading to a reduction in costs and a weight saving. In the production method proposed, the tools used are not subject to a high level of wear. The individual section limbs are continuously reliably assembled by the machine tool in a manner resistant to shearing, top tension, compression and tension. The method proposed makes it possible to produce exact lengths for a specific requirement as easily as with commercially available bar stock cut to length. The machining installations themselves are so reasonable that even relatively small companies can purchase them and are thus able to produce an unlimited number of their own desired sections from a few widths and thicknesses of strip steel which they can keep in stock or can easily produce themselves. In the method according to the invention for producing a metal section, the junctions are not weakened by bending and cracking forces but, by contrast, are strengthened by the cold work-hardening which is to be achieved during the microstructure-changing attachment, so that there is more likelihood of the remaining section limb material bending under load than of the join becoming detached. In addition, in the event of very high static demands, subsequent controlled partial or complete increase of the material strength of the respective joining zones is possible, such as for example by shot-peening, heat treatment, etc. The corners may be of virtually angular design without rounded portions or material shoulders, as a result of which a smooth joint contour can be produced right up to the abutting edges of the individual section limbs. The zone in which two section limbs are attached to one another in a microstructure-changing manner extends, even if it is intended to achieve high extraction forces, to zones which are of only small width, for example to 1 mm or even a smaller width in the case of metal sheets which are a few millimetres thick, so that there are no optical and technical drawbacks resulting from projections or protrusions at the attachment location. Also, the section limbs being machined in the method according to the invention may optionally be subjected to different additional machining and/or treatments before, during or after the machining, depending on the time at which the machining or treatment can be caried out most easily. The production method may also be used to add additional variants to existing ranges of sections, girders, pipes, corners, etc., by the microstructure-changing attachment of additional section limbs or workpieces. Different materials in a finished metal section result in advantages for subsequent recycling, since the individual section limbs can later be separated from one another again relatively easily. This may be advantageous if toxic materials such as lead are used or individual limbs are contaminated in a particular manner by radioactive radiation, chemicals, etc., or individual section limbs consist of particularly valuable materials such as, for example, platinum in catalysts.